1. Field of the Invention
The present invention relates to a focusing drive apparatus and, more particularly, to a focusing drive apparatus capable of manual focusing and automatic focusing.
2. Related Art
In handy cameras mainly for use in television broadcasting, a handy type of lens unit called “ENG lens” is used. The ENG lens has a focusing ring on the front side of a lens barrel. Focusing of the ENG lens can be performed by manually rotating the focusing ring.
A drive device called a drive unit is ordinarily provided on the lens barrel of the ENG lens. The focusing ring can be rotated in an electric drive manner by driving a motor provided in the drive unit, thus enabling focusing by electric drive. Therefore, the ENG lens can be used as an automatic focusing (AF) lens by providing an AF function in the drive unit or the like.
Even in the case of an AF lens, there is a need to enable manual focusing (MF) particularly in broadcasting as well as AF. For example, Japanese Patent Application Laid Open No. 2003-337278 discloses a device for changing the focusing mode between AF and MF by operating a certain switch. On the other hand, professional camerapersons ordinarily have a strong preference to perform MF by operating an operating member such as a focusing ring mechanically connected directly to a focusing lens group. In the above-described ENG lens, the focusing ring and the motor in the drive unit are connected by a clutch. This clutch is disengaged by operating a certain switch to enable an MF operation to be performed by means of the focusing ring.